We don't hear of Darcy dancing with Jane at the Netherfield Ball, and she has also spent several days in the same house.

Personally I think Darcy danced with Elizabeth because he wanted the pleasure of her company, not out of some sense of etiquette. It meant half an hour with her. You know my opinion that the mere failure to ask a girl to dance was not an insult to her as otherwise I must believe that Mr Knightley was insulting ladies in JA's _Emma_.